In an attempt to improve the resolution of LCD displays and to reduce the fabrication cost there is an effort underway to reduce the size of the pixels in active matrix liquid crystal display devices (AMLCD). This is particularly true of projection LCD's. These efforts have not been as successful as desired because of problems with aperture ratio and edge effects.
The pixel electrodes of LCD's are made of transparent conductive material, such as idium tin oxide (ITO), polysilicon or .alpha.Si. In addition to the pixel electrodes an LCD includes select lines, data lines, and solid state switching devices, which are used to connect the data lines to the pixel electrodes. An LCD also includes a black matrix to improve display brightness by preventing light from exiting between the pixles. The data lines, select lines, TFT's and black matrix are opaque. Aperture ratio is defined as the transparent area of the panel divided by the total area of the panel. This ratio becomes a problem as the pixel electrodes are made smaller because the opaque elements of the display remain approximately the same size. In high density displays such as projection displays, the opaque elements of the display may occupy up to 70% of total area leaving only 30% transparent. Hence, 70% of the light is lost and a lower quality granular image results. A structure which increases the percentage of light transparent area would constitute a marked advance in the art.
Small pixels are also more susceptible to edge effects caused by a non-planar surface and infringing electric fields. These edge effects degrade the contrast ratio and can lead to non-uniformities in the display.